The proposed research introduces a new tool for the mechanical characterization and separation of biological materials. The tool is based on the observation that an object in an immiscible host liquid, which is subjected to a sound field, wwll experience a steady force due to acoustic radiation pressure. We can adjust this ultrasonic force so that it balances the gravitational force on a object, thereby levitating it. We have measured the tensile strength of liquids, the elastic properties of liquids (including lipid oils), and the interfacial tension associated with the interface between two liquids. One important feature of acoustical levitation is the independence of the position of levitation on the size of the object being levitated for samples smaller than 2mm; the position of levitation depends strongly on the compressibility of the sample. Therefore, in addition to characterizing the mechanical properties of the samples, as desbribed above, our device can in principle separate samplls by their elastic property. This capability to separate by elastic property would be a unique contribution. This is contrasted with the complementary mechanical property of density, for which a great abundance of excellent equipment is available. Initially we propose to use and modify our levitation systems for the study of the mechanical properties of blood. In particular we are interested in measuring 1. the elastic propserties of red blood cells, 2. the elastic properties of red blood cell ghosts. 3. the tensile strength of red blood cells in the absence of shear stress, and 4. the interfacial tension of the r.b.c. membrane. We also hope to determine what degree of separation of blood components (red cells, white cells, plasma, etc.) can be achieved by acoustical levitation.